Macroreticular cation exchange beads and preparation of same

ABSTRACT

Process for preparing cation exchange resin having macroreticular structure, high surface area and lowered apparent density from a macroreticulated copolymer produced by copolymerizing a mixture of a monoethylenically unsaturated monomer and a polyethylenically unsaturated monomer dissolved in an organic liquid which is a solvent for said monomers but unable to substantially swell the resulting copolymer, and macroreticulated cation exchange resin beads produced by the process.

This is a division of application Ser. No. 749,526 filed July 12, 1958,now U.S. Pat. No. Des. 250,972.

This invention relates to a process for preparing copolymers and thecopolymers prepared thereby.

An object of this invention is the preparation of copolymers which arevaluable as absorbents for organic fluids. They are also valuable forthe separation of mixtures of organic fluids.

A further object of this invention is the preparation of copolymerswhich are particularly suitable intermediates for the preparation of ionexchange resins.

A further object of this invention is the preparation of intermediatesfor the preparation of ion exchange resins which, while highlycross-linked, still exhibit desirable ion exchange characteristics,i.e., the ion exchange rates are high, the regeneration efficiency isgood, etc.

A further object of this invention is the preparation of intermediateswhich are particularly suitable for the preparation of ion exchangeresins that are highly resistant to oxidation.

A further object of this invention is the preparation of copolymerswhich exhibit a high specific surface, so that ion exchange resinsprepared therefrom have much higher proportions of readily availableexchange sites than resins heretofore available.

A further object of this invention is the preparation of cross-linkedcopolymers which are intermediates for the preparation of ion-exchangeresins that have high moisture content even at high degrees ofcross-linking.

A further object of this invention is the preparation of cross-linkedcopolymers which are intermediates for the preparation of ion-exchangeresins which ion-exchange resins exhibit superior resistance to physicalstresses, such as produced, for instance, by osmotic shock, than hasheretofore been possible.

Another object of this invention is the preparation of cation exchangersof the sulfonic and carboxylic types as well as weak and strong baseanion-exchange resins.

It is well known in the prior art to use cross-linked copolymers ofmonovinylidene and polyvinylidene monomers as intermediates for theproduction of ion-exchange resins. Conversion of such copolymers tocation-exchange resins by sulfonation is set forth in U.S. Pat. No.2,366,007.

Although substantially insoluble sulfonated resins having high cationabsorptive capacities and possessing good ion-exchange properties may beprepared by the method of U.S. Pat. No. 2,366,007 it is difficult bysaid method to obtain a high yield of the sulfonated resin in the formof stable granules of sizes and physical form well adapted to use inusual ion-exchange processes, e.g., for the softening or thepurification of water. The difficulties which are encountered may besummarized as follows.

The copolymers of monovinyl- and polyvinylaromatic compounds, and alsotheir sulfonation products, are hard, brittle resins which aresusceptible to cracking, spalling, or shattering when subjected tointernal strain or to large external stresses. For most ion exchangepurposes, it is important that a major portion, e.g., 80 percent byweight or more, of the sulfonated resin be in the form of granules offrom 10 to 60, preferably from 20 to 40, mesh size, since smallerparticles tend to be washed from a bed of the resin during upflow ofwater through the bed and granules of larger sizes tend to developexcessive internal strains and to undergo shattering and spalling withformation of fine particles both during pre-conditioning for use in ionexchange processes and during use as an ion exchange agent in suchprocesses.

As set forth in U.S. Pat. No. 2,500,149, the sulfonation process can beimproved by swelling the copolymer in a solvent of specified propertiesprior to sulfonation. As this solvent must be imbibed readily by thecopolymer, it must be chosen from the class capable of dissolvingpolystyrene, such as chlorinated aliphatic hydrocarbons. The preferredmethod consists of forming the copolymer in the absence of such solvent,thereafter allowing such solvent to be imbibed.

While the process as set forth in U.S. Pat. No. 2,500,149 does overcomemany of the problems encountered in the sulfonation process, the cationexchange resin produced thereby still exhibits the general properties ofthe resins prepared by the process of U.S. Pat. No. 2,366,007, differingmainly in that the resin from the process of U.S. Pat. No. 2,500,149contains a higher percentage of whole beads. The resins are just assusceptible to fracture on osmotic shock and still exhibitde-cross-linking on being subjected to oxidative conditions and volumechanges when converted from one ionic form to another.

It has been claimed that many of these difficulties can be overcome byemploying the process set forth in British Pat. No. 785,157. In theprocess disclosed in this patent, a monovinyl monomer is copolymerizedwith a polyvinyl monomer and the copolymer so prepared is then reactedfurther to produce the desired ion exchange resin. The improvement inthe British Patent comprises partially pre-polymerizing the monovinylmonomer before adding the polyvinyl monomer. The same effects may beobtained by dissolving a pre-formed polymer in the monovinyl monomerbefore copolymerizing with the polyvinyl monomer. Ion exchange resinsformed from these copolymer beads are said to be much more resistant toshock, and an anion exchanger prepared therefrom was superior on colorremoval. There is no evidence that the resins exhibit any higherresistance to oxidative de-cross-linking than any of the other prior arttypes. There would appear to be another disadvantage to the cationexchange products produced by the process of the British Patent. Thecopolymer contains linear polymer chains, i.e. chains which are notcross-linked. These chains on sulfonation become at least partiallywater-solubilized and so can be leached from the resin. Thus, there canbe contamination of any fluid passing through the resin. Resins of thissame general type are also described by Abrams (J. Ind. Eng. Chem. 48,1469 et seq. (1956)).

In accordance with the present invention, unusual and completelyunexpected properties have been surprisingly found in the copolymerswhich result when a monoethylenically unsaturated monomer andpolyvinylidene monomers are suspension polymerized in in the presence ofcertain compounds. Characteristic of these compounds is the fact thateach is a solvent for the monomer mixture being copolymerized and exertsessentially no solvent action on said copolymer. For ease of referencehereinafter, such a compound will be termed "polymer precipitant" or,even more simply, "precipitant".

The ion-exchange resins prepared using said copolymers as intermediatesalso exhibit unusual and unexpected properties.

It is necessary that precipitants form a homogeneous solution with themonomer. Further requirements are that the precipitants must beincapable of exerting solvent action on or being imbibed by thecopolymer to any appreciable extent or the aforesaid unique propertieswill not be obtained in the copolymers produced. An additionalrequirement is that the precipitants must be chemically inert under thepolymerization conditions. A preferred class of precipitants are thosewhich are liquid under the polymerization conditions.

The determination of the most effective precipitant and the amountsrequired for the formation of a particular copolymer may vary from caseto case because of the numerous factors involved. However, althoughthere is no "universal" or single class of precipitants applicable toall cases, it is not too difficult to determine which precipitants willbe effective in a given situation. The requirements of solubility withthe monomer mixture and low or non-solubility in the copolymer can betested empirically and the solubilities of many monomers and copolymersare well known from publications and textbooks.

Cross-linked copolymers are generally insoluble, but they will absorb orimbibe liquids which might be considered as being good "solvents." Byimmersing the cross-linked copolymer in liquids and determining thedegree of swelling, a suitable precipitant can be chosen. Any liquidswhich are solvents for the monomer mixture and which give negligibleswelling of the copolymer will function as precipitants.

As a further guide in the selection of a suitable precipitant, referencemay be made to scientific literature, for instance as discussed inHildebrand and Scott, Solubility of Non-Electrolytes, 3d ed., N.Y.,1950. In general, it may be stated that sufficiently wide differences inthe solubility parameters of polymer and solvent, respectively, mustexist for the precipitant to be effective; and that, once an effectiveprecipitant has been located, the behavior of many other liquids may bepredicted from the relative position of the reference polymer andprecipitant in published tables, within the accuracy of such publishedinformation. Furthermore, if the solubility parameter of a given polymeroccupies an intermediate position in these tables, solvents with bothhigher or lower parameters may become effective.

A minimum concentration of any particular precipitant is required toeffect phase separation. This is comparable to the observation that manyliquid systems containing two or more components are homogeneous whensome components are present in only minor amounts; but if the criticalconcentration is exceeded, separation into more than one liquid phasewill occur. The minimum concentration of the precipitant in thepolymerizing mixture will have to be in excess of the criticalconcentration. The amounts in excess of such critical concentration canbe varied and they will influence to some extent the properties of theproduct so formed.

Too high a concentration of the precipitant may be undesirable forpractical reasons since the rate of copolymerization may decrease andthe space-time yields become low. In many cases, the amount ofprecipitant employed may be between 25 percent and 60 percent of thetotal weight of the monomer mixture and the precipitant.

The figure shows graphically the interdependence of crosslinker contentand precipitant level in achieving phase separation by the process ofthe present invention. Increasing amounts of either crosslinker orprecipitant tend to reduce the density of copolymer particles producedby suspension polymerization.

The effect of the concentration of the precipitant at a givencross-linker content and the effect of variations in the amount ofcross-linker on the precipitant requirements is shown in Table I. In thecase of tert-amyl alcohol and sec-butanol, the need for higherprecipitant concentrations as the amount of cross-linking decreases isclearly evident. With all three alkanols, the values given showconclusively that there is a definite concentration of precipitant belowwhich no phase separation occurs; and, without phase separation, theunusual and desirable properties of the products of this invention arenot obtained.

                  TABLE I                                                         ______________________________________                                        EFFECT OF CONCENTRATION OF PRECIPITANT                                        AND AMOUNT OF CROSS-LINKING OF A                                              STYRENE-DIVINYLBENZENE COPOLYMER                                              DIVINYLBENZENE              COPOLYMER                                         CONCENTRATION.sup.1                                                                          PRECIPITANT.sup.4                                                                          APPEARANCE.sup.2                                  ______________________________________                                         20            20% TAA.sup.3                                                                              Clear                                             20             35% TAA      P.S.                                              16             25% TAA      Clear                                             16             35% TAA      P.S.                                              9              30% TAA      Clear                                             9              40% TAA      P.S.                                              20             25% sec-butanol                                                                            Clear                                             20             30% sec-butanol                                                                            P.S.                                              15             25% sec-butanol                                                                            Clear                                             15             35% sec-butanol                                                                            P.S.                                              6              35% sec-butanol                                                                            Clear                                             6              40% sec-butanol                                                                            P.S.                                              15             23% n-butanol                                                                              Clear                                             15             35% n-butanol                                                                              P.S.                                              ______________________________________                                         NOTES:                                                                        .sup.1 Divinylbenzene Concentration is the percent of divinylbenzene in       the styrenedivinylbenzene copolymer based on the total weight of monomers     .sup.2 Copolymer appearance can be employed as a criterion of whether or      not phase separation (P.S.) has occurred. If the beads are clear, there i     no phase separation; when there is a small amount of phase separation, th     beads are translucent, and as the amount of phase separation increases,       the translucency increases. The examples of phase separation shown in thi     table represents substantially complete phase separation.                     .sup.3 TAA is tertamyl alcohol.                                               .sup.4 The percent precipitant is the percent based on the total weight o     the organic phase, i.e. weight of monomers plus weight of precipitant.   

While the use of a single precipitant facilitates recovery, purificationand recycling of the precipitant, mixtures of precipitants are withinthe scope of the present invention.

When suspension copolymerizing monomers, an additional factor must beconsidered, namely the solubility of the precipitant in the suspendingmedium. Since suspension polymerization of most ethylenicallyunsaturated monomers is generally conducted in aqueous media, mostfrequently it is the water-solubility of the precipitant which must beconsidered. While precipitants with water-solubilities as high as 15 to20 grams per 100 grams of water can be employed, a low water solubilityis preferred because of handling ease, ease of recovery, and processingeconomies. As is well-known, however, it is possible to decrease thewater-solubilities of compounds by adding salts to the aqueous phase.This method also may be employed to decrease the water-solubilities ofthe precipitants utilized so significantly in the present invention.

Introduction of the precipitant leads to two effects, the second effectundoubtedly depending on the first. By adding the precipitant to themonomer phase, the solubility in the monomer phase of any copolymerformed is decreased and the copolymer separates from the monomer phaseas it is formed. This phenomenon is known as "phase separation". As theconcentration of monomer in the polymerizing mass decreases due topolymerization, and as the concentration of resulting copolymerincreases, the precipitant is more strongly repelled by the copolymermass and is actually squeezed out of the copolymer phase leaving aseries of microscopic channels.

These microscopic channels are separate and distinct from the microporeswhich are present in all cross-linked copolymers as is well-known tothose skilled in the art (cf. Kunin, "Ion Exchange Resins", page 45 etseq., John Wiley & Sons, Inc., 1958). While said channels are relativelysmall in the commonly thought of sense, they are large when comparedwith the micropores hereinbefore referred to. Thus, as set forthhereinafter, the use of a precipitant results in the formation of anunusual and desirable structure. It is postulated that this "liquidexpulsion" phenomenon and the resulting reticular structure isresponsible for the unusual and unexpected properties of the resultantcopolymer. Since the rigidity of the polymer mass at the time ofprecipitant expulsion is important, it is not surprising that thedesirable properties obtained increase with increasing polyvinylidenecontent, i.e., increasing degrees of cross-linking. As a specificexample, using a sulfonated styrene-divinylbenzene copolymer, theprocess of the present invention is appreciably less effective belowabout 4% to 6% divinylbenzene content in the copolymer than it is athigher divinylbenzene levels. With this specific system, preferredeffects are obtained with a divinylbenzene content of from about 8% toabout 25%, based on the weight of the monomer mixture.

Because of the reticular structure as hereinbefore set forth, thesecopolymers have enhanced utility in the field of adsorbents for fluids,ion exchange resins, and for applications in which lower densitymaterials are desired. As hereinafter set forth, they can be subjectedto chemical transformation, the resultant structures displaying similaradvantages because of the reticular nature of the copolymers employed inthe preparation of said structures.

The terms "reticular" and "macroreticular", which are usedinterchangeably herein with the same intended meaning, relate to theunique structure of the polymers of the present invention produced bythe herein disclosed phase separation technique utilizing aprecipitating agent. Conventional prior art resins are essentiallyhomogeneous cross-linked "gels" wherein the only pore structure isdefined by molecular-sized openings between polymer chains. This type ofmolecular porosity is presently known in the art as "microporosity".Macroreticular resins, by contrast, contain significant non-gel porosityin addition to the normal gel porosity. The non-gel pores have beenseen, by electron micrographs, to be channels between agglomerates ofminute spherical gel particles. The prior art gel resin has a continuouspolymeric phase while the macroreticular resin is clearly shown toconsist of agglomerates of randomly packed microspheres with both acontinuous polymer phase and a continuous void phase. Thus theexpression "porous" as used herein refers to the channels or openingsbetween agglomerates of minute spherical particles.

The term "suspension polymerizing" is a term well-known to those skilledin the art and comprises suspending droplets of the monomer or monomermixture in a medium in which the monomer or monomer mixture issubstantially insoluble. This may be accomplished by adding the monomeror monomer mixture with any additives to the suspending medium whichcontains a dispersing or suspending agent, such as, for instance, in thecase of an aqueous suspending medium, the ammonium salt of astyrene-maleic anhydride copolymer, carboxymethyl cellulose, bentoniteor a magnesium silicate dispersion. When this medium is agitated, themonomer phase disperses into fine droplets, the size of the dropletsdepending on a number of factors, such as amount of dispersing agent,type and rate of agitation, etc. Agitation is continued untilpolymerization is complete. The polymerized droplets, generally termed"beads", are then separated from the suspending medium and furtherprocessed, if desired.

The suspension polymerization of ethylenically unsaturated monomers ormonomer mixtures, particularly those employed in the process of thepresent invention, generally uses aqueous suspending media.

When employing water-soluble ethylenically unsaturated monomers,however, it is not possible to use aqueous suspending media unless thesolubility of the monomers is such that they can be salted out. If it isnot possible to salt out the monomers, then compounds in which themonomers are insoluble must be employed as suspending media. Thecompounds used must be chemically inert in the sense that they do notinterfere with the polymerization reaction. Aliphatic hydrocarbons aretypical of such media.

It is well-known that oxygen acts as an inhibitor of free radicalpolymerizations and should, therefore, be excluded. The preferredembodiments of this invention effect polymerization under substantiallyanaerobic conditions.

Suitable catalysts which provide free radicals which function asreaction initiators include benzoyl peroxide, tert-butyl hydroperoxide,cumene peroxide, tetralin peroxide, acetyl peroxide, caproyl peroxide,tert-butyl perbenzoate, tert-butyl diperphthalate, methyl ethyl ketoneperoxide, etc.

The amount of peroxidic catalyst required is roughly proportional to theconcentration of the mixture of monomers. The usual range is 0.01% to 3%of catalyst with reference to the weight of the monomer mixture. Thepreferred range is from 0.2% to 1.5%. The optimum amount of catalyst isdetermined in large part by the nature of the particular monomersselected, including the nature of the impurities which may accompanysaid monomers.

Another suitable class of free radical generating compounds are the azocatalysts. There may be used, for example, azodiisobutyronitrile,azodiisobutyramide, azobis(α,α-dimethylvaleronitrile),azobis(α-methylbutyronitrile), dimethyl, diethyl, or dibutylazobis(methylvalerate). These and other similar azo compounds serve asfree radical initiators. They contain an --N═N-- group attached toaliphatic carbon atoms, at least one of which is tertiary. An amount of0.01% to 2% of the weight of monomer or monomers is usually sufficient.

Another method of effecting copolymerization of the compositions of thepresent invention is by subjecting the reaction mixture to ultravioletlight in the presence of suitable catalysts at ambient or slightlyelevated temperatures. Such catalysts include benzoin,azoisobutyronitrile, etc.

Suitable monoethylenically unsaturated monomers, includingmonovinylidene monomers, include the following: methyl acrylate, ethylacrylate, propyl acrylate, isopropyl acrylate, butyl acrylate,tert-butyl acrylate, ethylhexyl acrylate, cyclohexyl acrylate, isobornylacrylate, benzyl acrylate, phenyl acrylate, alkylphenyl acrylate,ethoxymethyl acrylate, ethoxyethyl acrylate, ethoxypropyl acrylate,propoxymethyl acrylate, propoxyethyl acrylate, propoxypropyl acrylate,ethoxyphenyl acrylate, ethoxybenzyl acrylate, ethoxycyclohexyl acrylate,and the corresponding esters of methacrylic acid, styrene, vinyltoluene,vinylnaphthalene, and similar unsaturated monomers.

In the case of the acrylic esters, a preferred embodiment employs loweraliphatic esters of acrylic acid in which the aliphatic group containsfrom one to five carbon atoms. This is a particularly preferredembodiment when the copolymers therefrom are to be employed asintermediates in the preparation of either carboxylic cation exchangeresins or anion exchange resins. In the preparation of both thecarboxylic exchanger and the anion exchanger, the ester group isreplaced. Thus, the practical choice is methyl or ethyl acrylate.

Another class of suitable monovinylidene monomers include themonovinylidene ring-containing nitrogen heterocyclic compounds, such asvinylpyridine, 2-methyl-5-vinylpyridine, 2-ethyl-5-vinylpyridine,3-methyl-5-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, and2-methyl-3-ethyl-5-vinylpyridine, 2-methyl-5-vinylquinoline,4-methyl-4-vinylquinoline, 1-methyl- or 3-methyl-5-vinylisoquinoline andvinylpyrrolidone.

Copolymers of the above monomers with monovinylene compounds, such asdialkyl maleates, dialkyl fumarates, dialkyl crotonates, dialkylitaconates, and dialkyl glutaconates, are also possible.

Suitable polyvinylidene compounds include the following: divinylbenzene,divinylpyridine, divinyltoluenes, divinylnaphthalenes, diallylphthalate, ethylene glycol diacrylate, ethylene glycol dimethacrylate,divinylxylene, divinylethylbenzene, divinylsulfone, polyvinyl orpolyallyl ethers of glycol, of glycerol, of pentaerythritol, of mono-,or dithio- derivatives of glycols, and of resorcinol; divinylketone,divinylsulfide, allyl acrylate, diallyl maleate, diallyl fumarate,diallyl succinate, diallyl carbonate, diallyl malonate, diallyl oxalate,diallyl adipate, diallyl sebacate, divinylsebacate, diallyl tartrate,diallyl silicate, triallyl tricarballylate, triallyl aconitate, triallylcitrate, triallyl phosphate, N,N'-methylenediacrylamide, N,N'-methylenedimethacrylamide, N,N'-ethylenediacrylamide, 1,2-di(α-methylmethylenesulfonamido)ethylene, trivinylbenzene, trivinylnaphthalene, andpolyvinylanthracenes.

Particularly preferred polyvinylidene monomers, commonly known as"cross-linkers", include the following: polyvinylaromatic hydrocarbons,such as divinylbenzene and trivinylbenzene, glycol dimethacrylates, suchas ethylene glycol dimethacrylate, and polyvinyl ethers of polyhydricalcohols, such as divinoxyethane and trivinoxypropane.

The ratio of the monovinylidene monomers to the polyvinylidene monomersmay be varied widely within the scope of the present invention,depending on the use for which the copolymer is intended. As iswell-known in the art, the polyvinylidene monomers function ascross-linking agents by bridging two linear polymer chains. The ratio ofthe polyvinylidene to monovinylidene monomers is an indication of theamount of cross-linking present in the copolymer. It is important tocontrol accurately the ratio of polyvinylidene monomers tomonovinylidene monomers, since the degree of cross-linking has aprofound effect on the physical properties of the product. The effectsof the degree of cross-linking show up strikingly when ion exchangeresins are prepared from the copolymers. If a monovinylaromatichydrocarbon is used as the monovinylidene monomer, and a divinylaromatichydrocarbon, such as divinylbenzene, is used as the polyvinylidenemonomer, a cross-linked polystyrene is formed on copolymerization. Thiscopolymer can be sulfonated either with sulfuric acid, oleum, sulfurtrioxide, or chlorosulfonic acid to form a cation exchanger or it may bechloromethylated and aminated to form an anion exchanger.

The degree of cross-linking of the copolymer controls to a large extentthe properties of the ion exchange resins produced therefrom, whetherthey be cation or anion exchangers. If the degree of cross-linking betoo high, then the ion exchange resins therefrom will have too slow anexchange rate and too low a moisture content. If the degree ofcross-linking of the copolymer be too low, then the resins produced willbe deficient in oxidation resistance and will fail prematurely inservice. Furthermore, a resin with a low degree of cross-linking alsoexhibits swelling when converted from one ionic form to another and alsoexhibits lower ion selectivity than resins with higher degrees ofcross-linking. Thus, under prior art conditions, it was necessary torestrict the amount of cross-linking comonomer used in order to obtain asatisfactory rate of ion adsorption. This invariably meant compromisingon oxidation resistance and, hence, the stability of the resin inservice. Means have long been sought which would make possible theemployment of high ratios of cross-linking agent to obtain the desiredstability without being penalized with regard to the rate of ionadsorption and other ion-exchange properties as hereinbefore set forth.

It has now been found possible to achieve excellent resistance tooxidation by employing a high ratio of cross-linking monomer whileretaining the desired ion-exchange properties. This can be effected if amixture of a polyvinylidene monomer and monoethylenically unsaturatedmonomer is suspension copolymerized in the presence of a precipitant inaccordance with the present invention. As set forth herein, the amountof cross-linking monomer employed in the reaction mixture also affectsthe ratio of the precipitant which must be employed to get the desiredeffect. Furtheremore, the ratio will vary with the chemical identity ofthe cross-linker. The cross-linked copolymers produced by the process ofthis invention are particularly suitable as intermediates for use in thepreparation of ion-exchange resins, both anion and cation types, whetherof the character having homofunctional or mixed-functional groups.

The process of the present invention is particularly applicable in thesuspension copolymerization of ethylenically unsaturated monomers, sincesuspension copolymerization, when conducted under the conditions ashereinafter set forth, produces spherical beads, the size of which canbe controllably varied over wide ranges. Such beads are particularlysuitable as intermediates for the preparation of ion exchange resins. Asaforesaid, such resins may be of the anion and cation types.

As set forth hereinbefore, the chemical character of the precipitant mayvary appreciably depending on the monomer mixture which is used. Whenemploying aromatic hydrocarbon type monomers, such as, for instance,styrene and divinylbenzene, alkanols with a carbon atom content of fromabout 4 to about 10 will effect the desired phase separation and theaccompanying liquid expulsion when used in amounts of from about 30% toabout 50% of the total weight of monomers and precipitant.

Higher saturated aliphatic hydrocarbons, such as heptane, isooctane, andthe like may be employed as precipitants for aromatic hydrocarbonsystems, such as styrene and divinylbenzene. The amounts employed can bevaried from about 30% to about 50% of the total weight of the monomersand precipitant.

When employing acrylic esters as said monovinylidene monomers, alkylesters can be effectively employed as precipitants. Typical estersinclude n-hexyl acetate, 2-ethylhexyl acetate, methyl oleate, dibutylsebacate, dibutyl adipate and dibutyl carbonate. The esters must have acarbon atom content of at least 7. The concentrations required will varysomewhat with the ester being used but from about 30% to about 50% onthe combined weight of the monomers and the precipitant will effectivelycause the desired phase separation and the formation of a reticularstructure within the polymerized mass.

Saturated higher aliphatic hydrocarbons, such as heptane, isoctane, andthe like may be employed as precipitants when employing acrylic estersas the monovinylidene monomers. The amounts employed can be varied fromabout 25% to about 50%.

When employing ring-containing nitrogen heterocyclic compounds, such asvinylpyridine and substituted vinylpyridines, as the monovinylidenemonomers, higher saturated aliphatic hydrocarbons are suitable asprecipitants. Typical examples are heptane, isooctane, and the like, andthey can be employed in amounts varying from about 15% to about 45%.

The copolymers of the present invention are valuable as absorbents fororganic fluids because of their very high specific surface. Indicativeof their reticular structure is the rate of absorption of fluids. A 20%divinylbenzene-styrene resin prepared by the process of the presentinvention was immersed in benzene and reached equilibrium within oneminute. In contrast, a 9% divinylbenzene-styrene resin, prepared byprior art process, required sixteen hours to reach equilibrium, this inspite of its very much lower divinylbenzene content.

Preferential absorption of fluids by copolymers can be determined byimmersing the copolymer in a mixture of fluids and determining thecomposition of the external phase at any given time after immersion. Amixture of benzene and heptane, containing 48.6% benzene, was prepared.A sample of a 20% divinylbenzene-styrene copolymer prepared by theprocess of the present invention was immersed in the benzene-heptanemixture. After two minutes immersion, the composition of the liquidphase was determined. It was 44.4% benzene, showing preferentialabsorption of benzene by the copolymer. Under the same conditions, the9% divinylbenzene copolymer prepared by a prior art process showed noabsorption of organic fluid and thus no change in the composition of theliquid phase.

A preferred embodiment of this invention employs a monovinyl aromatichydrocarbon as the monovinylidene monomer, a polyvinyl aromatichydrocarbon as the polyvinylidene monomer, and an alkanol with a carboncontent of C₄ to C₁₀ as the precipitant. Thus, styrene may be used asthe monovinylidene monomer, divinylbenzene or trivinylbenzene as thepolyvinylidene monomer, and tert-amyl alcohol as the alkanol. Normalbutanol, sec-butanol, 2-ethylhexanol, and decanol also function well asprecipitants. The quantities of alkanol required are from about 30% toabout 50% of the weight of the monomer mixture and the alkanol with theleast amount of precipitant being required at the highest percentage ofcross-linking. The mixture of the three compounds is free radicalaqueous suspension copolymerized in the presence of a suspending agentand under controlled agitation to produce copolymer beads with adiameter ranging from about 0.35 to about 1.2 mm. The beads are washedwith water, dried, and then subjected to sulfonation using concentratedsulfuric acid, oleum, sulfur trioxide or chlorosulfonic acid assulfonating agent. The resulting cation exchange resin is washed withwater until substantially free from water solubles. As statedhereinbefore, the effects of the process of the present invention aremost marked when a higher level of cross-linking agent is employed, andwith the styrene-divinylbenzene system, a level of 8% to 25% ofdivinylbenzene, based on the total weight of monomer mix, gives thepreferred results.

A comparison of the exchange resins prepared by using precipitants inaccordance with the present invention with resins of exactly the samecomposition except for the omission of such precipitants shows clearlythe unexpected and improved properties obtained by the novel process ofthe present invention. As specific examples, styrene-divinylbenzenebeads containing 20% divinylbenzene were prepared by the two processes,i.e., a "standard" suspension polymerization reaction without alkanoland by the methods of the present invention employing tert-amyl alcohol.The "standard" copolymer beads had a density in water of 1.047 whereasthe beads prepared by the liquid expulsion process had a density inwater of 0.866. The measurement of the true densities of both beadsshowed no essential difference in the values. Comparison of the apparentdensities of the two copolymers showed essentially no voids ormicroscopic channels in the "standard" and approximately 17.5% voids inthe beads prepared by the liquid expulsion process.

Low apparent densities, indicative of the presence of the microscopicchannels hereinbefore described, are characteristic of the copolymersprepared according to the present invention. The densities decrease asthe amount of cross-linking increases and also decrease as the amount ofprecipitant increases. Both of these effects are clearly demonstrated bythe data in Table II. Similar results are presented graphically in theFIGURE.

The apparent densities, as listed in the specification, were determinedby pyenometric methods, using specially designed pyenometers and watercontaining 1 ppm of a non-ionic wetting agent as the contacting fluid.The reproducibility of the test method was demonstrated by repeatedmeasurement.

It is assumed that the contacting fluid fills the voids between the beadparticles but not the microscopic channels within the bead particlesthemselves. This is supported by the observation that the beads remainafloat indefinitely. In solvents which swell the polymer particles,however, such as ethylene dichloride, the channels within the beadparticles are filled by the contacting fluid or such channels may beclosed so that density values of the order of the standard type bead areobtained.

                  TABLE II                                                        ______________________________________                                        Densities of Styrene-Divinylbenzene L.E..sup.1 Resins                         Percent              Percent   Density of Beads                               DVB.sup.2                                                                             Precipitant  Solvent   in Water                                       ______________________________________                                        20      --           --        1.047 ± .001                                10      TAA.sup.3    35        1.020 ± .000                                12      TAA          35        1.017 ± .001                                15      TAA          35        0.984 ± .000                                18      TAA          35        0.917 ± .001                                30      TAA          35        0.730 ± .002                                50      TAA          35        0.620 ± .002                                20      TAA          20        1.042 ± .003                                20      TAA          30        .936 ± .005                                 20      TAA          35        .866 ± .003                                 20      TAA          38        .704 . .005                                    20      TAA          40        .626 ± .004                                 20      TAA          50        .411 ± .000                                 20      TAA          60        .34 ± .02                                   20      Iso-octane   20        1.016 ± .002                                20      Iso-octane   30        .781 ± .007                                 20      Iso-octane   40        .642 ± .000                                 20      Iso-octane   50        .338 ± .000                                 20      2-ethylhexanol                                                                             40        .734 ± .001                                 20      BuOH-2       40        .501 ± .001                                 ______________________________________                                         NOTE:                                                                         .sup.1 L.E. resins are resins prepared using the liquid expulsion             technique of the present invention.                                           .sup.2 DVB is divinylbenzene.                                                 .sup.3 TAA is tertamyl alcohol.                                          

When converted to a sulfonic acid type cation-exchange resin ashereinbefore described, the 20 percent divinylbenzene copolymer preparedusing a precipitant exhibits a completely unexpected and valuablecombination of properties. The resin is remarkably resistant to physicalstresses, such as the stresses caused by osmotic shock. The resin can bedried and dropped into water with substantially no physical breakdown.The moisture content, exchange rate, and regeneration efficiency of theaforementioned 20 percent divinylbenzene resin when equilibrated withwater is equivalent to that of a "standard" resin, prepared withoutprecipitant, containing only 9 percent divinylbenzene.

When anion-exchange resins are prepared from copolymers prepared by themethod of the present invention, it is found that they exhibit excellentcolor removal properties, even at relatively high cross-linker content.They also do not change volume appreciably on conversion from one ionicform to another. An ion-exchange resins prepared from copolymersprepared without precipitant are deficient in color removal properties,and their decolorizing capacity decreases rapidly as the cross-linkercontent increases. In order to obtain sufficient decolorizing capacityto make the resins useful, it is necessary to use low levels ofcross-linkers; and these resins change volume excessively on conversionfrom one ionic form to another. These excessive volume changes result inphysical breakdown of the resins in use.

Methods of preparing anion-exchange resins from copolymers are set forthin U.S. Pat. No. 2,591,573, and these methods can be employed withcopolymers of the present invention. They comprise chloralkylating astyrene-divinylbenzene copolymer and subsequently aminating thechloralkylated copolymer.

A wide variety of amines can be employed in the amination reaction.Thus, primary, secondary, and tertiary alkylamines or arylamines can beemployed. Polyalkylenepolyamines can also be used successfully. Typicalpolyalkylenepolyamines include ethylenediamine, diethylenetriamine,triethylenetetramine, tetraethylenepentamine, propylenediamine, and thelike. Aminoalcohols such as dimethylaminoethanol can also be usedsuccessfully.

A preferred embodiment of this patent employs a trialkylamine as theaminating agent, thus producing quaternary anion exchangers. The alkylradical does not generally contain more than 4 carbon atoms, withtrimethylamine being the preferred amine.

Another preferred embodiment of this invention employs copolymerizationof styrene as the monovinylidene monomer, divinylbenzene as thepolyvinylidene monomer, and an alkanol with 4 to 10 carbon atoms as theprecipitant. Chlormethylation of the resulting copolymer is effectedwith chlormethyl ether and trimethylamine is employed as the aminatingagent. A preferred range of divinylbenzene contents is from about 4percent to about 15 percent.

A styrene-divinylbenzene copolymer containing 20 percent divinylbenzeneand prepared according to the process of the present invention wasnitrated with nitric acid and the resulting nitrated polymer was reducedto the corresponding amino polymer by treatment with a tin-hydrochloricacid mixture, such a reduction procedure being well known to thoseskilled in the art. The aminopolymer exhibited weak base anion-exchangeproperties.

Another preferred embodiment of the present invention employs alkyl oralkoxy acrylates as the monovinylidene monomers, a polyvinylaromatichydrocarbon as the polyvinylidene monomer, and an alkyl ester with acarbon atom content of greater than 7 as precipitant. Thus, methylacrylate may be used as the monovinylidene monomer, divinylbenzene ortrivinylbenzene as the polyvinylidene monomer and 2-ethylhexyl acetateas the precipitant. At 10 percent divinylbenzene content (based on thetotal weight of the polymerizable monomers present) and at 30 percent of2-ethylhexyl acetate (based on the total weight of the organic phase),free radical aqueous suspension polymerization produced white beadswhich were characterized by resistance to physical breakdown on furtherchemical processing. Hydrolysis produced a carboxylic cation exchangerwith substantially no decrease in bead integrity. Similar retention ofphysicals is noted on aminolysis of the copolymer to produce anionexchangers.

The amines which can be employed in the aminolysis reaction must containat least two amino groups, at least one of which is a primary aminogroup. The primary amino groups react with the ester groups in thecross-linked copolymer to form amido groups. These amido groups,however, do not in themselves have anion-adsorbing properties. Thegroups which do adsorb anions are the other amino groups which arepresent in the amino compound. These groups can be primary, secondary,or tertiary. Very satisfactory amino compounds include the following:Propylenediamine; imino bispropylamine of the formula

    NH.sub.2 --C.sub.3 H.sub.6 --NH--C.sub.3 H.sub.6 --NH.sub.2

hydroxyethyldiethylenetriamine of the formula

    NH.sub.2 --C.sub.2 H.sub.4 --NH--C.sub.2 H.sub.4 --NH--C.sub.2 H.sub.4 --OH

N-aminopropylmorpholine, N-aminoethylmorpholine, anddimethylaminopropylamine which are particularly valuable because theresins made from these compounds are easily converted to strongly basicquaternary ammonium anion-exchange resins; diethylenetriamine;triethylenetetramine; tetraethylenepentamine; and the like.

A preferred range of divinylbenzene contents when employed in the systemin which acrylic esters are used as the monovinylidene monomers is fromabout 5 percent to about 25 percent.

When similar resin compositions are prepared in the absence of aprecipitant, the products of hydrolysis or aminolysis are usuallyextensively cracked and fragmented. Furthermore, the process of crackingand fragmentation of the resin particles continues in use, resulting,eventually, in complete physical disintegration of the resin to auseless powder.

Another embodiment of the present invention employs a vinylpyridine asthe monovinylidene monomer, a polyvinylaromatic hydrocarbon as thepolyvinylidene monomer and a saturated higher aliphatic hydrocarbon asthe copolymer precipitant. Thus, 2-methyl-5-vinylpyridine was suspensioncopolymerized with divinylbenzene, using iso-octane as the copolymerprecipitant. The resulting copolymer exhibited anion-exchangeproperties, but was too weak a base to be of practical utility. Thecopolymer was quaternized by reacting it with an alkyl halide such asmethyl chloride, methyl iodide, or dimethyl sulfate. This quaternizedcopolymer was a strongly basic anion exchanger. When employing analkylsubstituted vinylpyridine as the monovinylidene monomer anddivinylbenzene as the polyvinylidene monomer, preferred ranges ofdivinylbenzene content are from 5 percent to 25 percent, based on thetotal weight of the monomers.

An outstanding characteristics of the ion-exchange resins prepared fromcopolymers prepared by the process of the present invention is theincreased resistance to oxidative degradation. This is an extremelyimportant property in an ion-exchange resin, since it is one of the keyproperties which control the stability or "life" of the resin inservice. An accelerated test has been devised to determine the oxidationresistance of cation-exchange resins of the sulfonic acid type producedby the sulfonation of copolymers of styrene and divinylbenzene atvarying divinylbenzene levels; it comprises contacting the copper formof the resin with aqueous sodium hypochlorite solution and determiningthe salt-splitting cation capacity after each contact. (For method ofdetermining salt-splitting cation capacity, see Kunin, Ion ExchangeResins (John Wiley & Sons, 1958], p. 342 et seq.)

The details of this oxidation resistance test are as follows: A one-gramsample of the sodium form of the resin, previously screened to a -20 to+25 mesh size, was converted to the hydrogen form by treatment with anexcess of 4 percent hydrochloric acid, rinsed with deionized water andits salt-splitting cation capacity determined. After rinsing again withdeionized water, it was converted to the copper form by treatment withan excess of 4 percent copper sulfate solution. It was rinsed withdeionized water and contacted with 200 ml. of 5.25 percent sodiumhypochlorite solution at 30° C. for 16 hours. It was again rinsed withdeionized water, converted to the hydrogen form by treatment with anexcess of 4 percent hydrochloric acid, rinsed, and its salt-splittingcation capacity determined. The cycle can be repeated until the loss ofcapacity is so great that the resin is rendered useless.

Destruction of the resin by oxidation is shown by a loss insalt-splitting cation capacity. The results of this acceleratedoxidation resistance test as applied to a number of resin samples areshown in Table III.

                  TABLE III                                                       ______________________________________                                                     Per Cent Loss of S.S.C.C..sup.2 of                               Per Cent     Original Sample After Contacts                                   Divinylbenzene                                                                             1         2          3                                           ______________________________________                                         9, L.E.type.sup.1                                                                         3.7       12.7       22.3                                         9, L.E. type                                                                              5.0       8.7        13.1                                        12, L.E. type                                                                              4.2       14.6       20.2                                        20, L.E. type                                                                              1.0       4.1        5.2                                         20, L.E. type                                                                              1.1       8.0        5.3                                          9, Std. type.sup.3                                                                        33        79         82                                          10.5, Std. type                                                                            26.4      71.9       83.7                                        12.5, Std. type                                                                            13.6      50.9       83.3                                        ______________________________________                                         NOTES:                                                                        .sup.1 L.E. type is cation exchanger prepared from copolymer prepared wit     precipitant by the process of the present invention.                          .sup.2 S.S.C.C. is saltsplitting cation capacity.                             .sup.3 Standard type is cation exchanger prepared from copolymer prepared     without precipitant.                                                     

Another indication of the physical strength of ion-exchange resins istheir physical stability when subjected to alternate wetting and dryingcycles. Such cycles subject the resin particles to severe stresses dueto the appreciable swelling which occurs on wetting and the comparibleshrinkage which occurs on drying. Many resins will break down intouseless fine particles on one such cycle. A test was devised todetermine the amount of fines generated by such cycles on differentresin samples. The details of the test are as follows:

The screened resin samples to be tested were placed in aluminum foilweighing pans around the outside of a turntable. A single pin hole waspunched in each pan to connect it with a paper wick to drain water fromthe pan. The pans were spaced evenly around the top shelf of theautomatic turntable with a small beaker on the second shelf under eachpan to catch the water that drained out. An infrared lamp was positionedover one side of the turntable and an intermittent dispenser waspositioned to deliver water one-third of a cycle beyond the drying lamp.This dispenser was timed to deliver 10 ml. of water every time a samplepan passed under it. This water slowly drained through the pin holeduring the next one-third cycle. By the time the sample again arrivedunder the infrared lamp, it had drained and was ready for drying. Theentire cycle for each sample required approximately two hours, a timecycle which permitted approximately ten minutes drying time per sample.This time is known to reduce the residual moisture content of sulfonicresins to less than 10 percent.

Two grams wet samples of sodium-form resin of known moisture contentwere weighed into the aluminum dishes. In all cases, the sample had beenpre-screened to give a definite screen cut. Samples were added andremoved from the cycles in the portion of the cycle just after theaddition of water. The samples were re-screened every third cycle. Thematerial passing the smaller of the original two screens was collectedand its dry weight determined in each case. The material still in theoriginal particle size range can be returned to the pans for additionalcycling, if desired. The dry weight of the fins was determined andexpressed as a percentage of the original dry weight of the sample.

The results of a series of such tests are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        Per Cent DVB.sup.1                                                                       Mesh Cut    Per Cent Fines Developed.sup.4                         ______________________________________                                         9, Std. type.sup.2                                                                      -20 to +30  51.8                                                              -30 to +40  14.3                                                   12.5, Std. type                                                                          -20 to +30  63.0                                                              -30 to +40  22.8                                                   15, L.E. type.sup.3                                                                      -20 to +30  2.0                                                    20, L.E. type                                                                            -20 to +30  3.7                                                               -30 to +40  1.4                                                    ______________________________________                                         NOTES:                                                                        .sup.1 DVB is divinylbenzene                                                  .sup.2 Standard (Std.) type is sulfonic type cation exchanger prepared        from copolymer prepared without precipitant.                                  .sup.3 L.E. type is sulfonic type cation exchanger prepared from copolyme     prepared with precipitant by the process of the present invention.            .sup.4 Figures given represent the percentage fines developed after three     (3) cycles. Minor variations in the low figures are not considered to be      significant. A value below five (5) is considered to be excellent.       

One undesirable characteristic of carboxylic cation exchangers derivedfrom cross-linked acrylic ester copolymers by hydrolyzing saidcopolymers is the poor resistance to physical shock which they exhibit.On changing from one ionic form to another, they exhibit appreciablechange in particle size which changes set up stresses within the resinparticle. With some resins, the particle breakdown may occur during theprocessing required to produce the final product. In other cases, thebreakdown occurs during use. In both cases, the net result is a finelydivided powder, unless for its intended purpose.

An accelerated test was developed to determine the relative resistanceto shock of the various resins which comprised contacting a screenedmoist resin sample in 1 N sodium hydroxide, rinsing with deionized waterand then contacting with 1 N hydrochloric acid and then rinsing withdeionized water. The cycle was repeated every four minutes. At anypredetermined time, the samples were re-screened and the portion of thesample which passed through the smaller of the two original screens wascollected and weighed. Typical carboxylic cation exchangers prepared bythe hydrolysis of methyl acrylate-divinylbenzene copolymers preparedwithout precipitant were subjected to the acid-base cycling testhereinbefore described. Using a -20 to +30 mesh cut and cycling 15times, a loss of 33 percent was observed. A methylacrylate-divinylbenzene copolymer of the same composition as the onedescribed hereinbefore, but prepared with a precipitant in accordancewith the process of the present invention was hydrolyzed to thecorresponding carboxylic cation exchanger and subjected to the samecycling test. The loss due to physical breakdown was negligible, being0.55 percent. The results of these tests clearly show the markedsuperiority of the carboxylic cation exchangers prepared from thecopolymers of the present invention.

The following examples set forth certain well-defined instances of theapplication of this invention. They are not, however, to be consideredas limitations thereof, since many modifications may be made withoutdeparting from the spirit and scope of this invention.

Unless otherwise specified, all parts are parts by weight.

EXAMPLE I

A mixture of styrene (121.6 g.), technical divinylbenzene (38.4 g.containing 50 percent active ingredient), 87 g. of tert. amyl alcoholand 1 g. of benzoyl peroxide was charged to a solution of 6.5 g. ofsodium chloride and 0.5 g. of the ammonium salt of a commercial styrenemaleic anhydride copolymer in 174 g. of water. The mixture was agitateduntil the organic components were dispersed as fine droplets and thenheated to 86°-88° C. for 6 hours.

The resultant polymer pearls were filtered and washed with water andfreed from excess water and amyl alcohol by drying at elevatedtemperature. The product was obtained in the form of white opaquespherical or spheroidal particles amounting to 145 g. When the driedproduct was dropped into a fluid such as hexane, fine bubbles were seento rise from the immersed particles due to displacement of air heldwithin the void spaces of the resin by the organic fluid.

EXAMPLE II

A mixture of styrene (360 g.), technical divinylbenzene (240 g. of 50percent divinylbenzene concentration), benzoyl peroxide (3.8 g.) andsecondary butanol (400 g.) was charged to a solution of 27 g. of sodiumchloride and 3 g. of the ammonium salt of a commercial styrene-maleicanhydride copolymer in 722 g. of water. Agitation was applied so thatthe organic phase was dispersed in the form of fine droplets. Thepolymerization was carried out by heating at 86°-92° C. for six hours.Steam was then passed through the reaction mixture and an azeotropicmixture of secondary butanol and water was removed overhead. The beadsso formed were then filtered and washed with water and then dried forfive hours at 125° C. There was obtained 543 g. of white opaque polymerin the form of spherical or spheroidal particles.

The bulking volume of this material was compared with the analogousproduct prepared in the absence of secondary butanol. Weighed quantitiesof each resin were transferred to graduated cylinders and the productssettled by tapping. The material prepared in the presence of butanol hada bulking volume of 2.9 ml./g. whereas a product of the same compositionbut prepared without butanol had a bulking volume of only 1.55 ml./g.

EXAMPLE III

Sulfuric acid (99 percent, 750 g.) and the dried product (75 g.)prepared as set forth in Example I were charged to a flask and heatedwith stirring at 118° to 122° C. for 6 hours. The mixture was thencooled to about 20° C. and diluted with water. The solid product wasfiltered and washing was continued to remove all soluble material.

The drained product, amounting to 301 g. of water swollen sulfonatedproduct in the hydrogen form, was of translucent to opaque appearanceand consisted nearly entirely of uncracked whole spherical particles incontrast to the heavy shattering and spalling encountered with polymerparticles prepared in the absence of the conditions provided by theinvention. The product was converted to the sodium form by the use of asmall excess of sodium hydroxide.

The sodium form of the resin had a moisture content of 51 percent, asalt splitting capacity of 4.6 meq./g. dry or 1.8 meq./ml. in the wetcondition. The density was 49 lbs/cu. ft.

The polymeric product prepared as set forth in Example II was sulfonatedin an analogous manner. It had an exchange capacity of 4.6 meq./g. dryor 2.0 meq./ml. wet, a moisture content of 46 percent and a density of52 lbs./cu. ft., all values referring to the sodium form of the resin.

EXAMPLE IV

(A) A mixture of styrene (88 g.), trivinylbenzene (12 g.), benzoylperoxide (1 g.) and tert-amyl alcohol (54 g.) was dispersed in asolution of 7 g. of sodium chloride and 0.6 g. of the ammonium salt of acommercial styrene-maleic anhydride copolymer in 185 g. of water. Thepolymerization was carried out by heating at 86°-90° C. for 5 hours. Thebeads so formed were filtered, washed with water and then dried 5 hoursat 125° C. There was obtained a yield of 99 g. of white opaque polymerin the form of spherical or spheroidal particles.

(B) The dried product (70 g.) prepared as set forth in part A andsulfuric acid (99 percent, 800 g.) was heated with stirring at 118°-122°C. for 7 hours. The mixture was then cooled to about 35° C. and dilutedwith water. The solid product was filtered, washed well with water toremove water soluble products, and drained. There remained 273 g. ofwater-swollen sulfonated product in the hydrogen form. The product wassubstantially completely in the form of uncracked whole sphericalparticles of translucent to opaque appearance.

EXAMPLE V

(A) A mixture of styrene (100 g.), technical divinylbenzene (43 g. of 50percent concentration), benzoyl peroxide (0.9 g.) and secondary butanol(48 g.) was charged to a solution of 7 g. of sodium chloride and 0.6 g.of the ammonium salt of a commercial styrene-maleic anhydride copolymerin 212 g. of water. Agitation was applied so that the organic phase wasdispersed in the form of fine droplets. The polymerization was carriedout by heating at 86°-90° C. for 5 hours. The beads so formed werefiltered, washed with water, and then dried for 5 hours at 125° C. Therewas obtained 136 g. of clear, colorless polymer in the form of sphericalor spheroidal particles.

(B) In a similar preparation, a mixture of styrene (100 g.), technicaldivinylbenzene (43 g. of 50 percent concentration), benzoyl peroxide(0.9 g.) and secondary butanol (62 g.) was charged to a solution of 7 g.of sodium chloride and 0.6 g. of the ammonium salt of a commercialstyrene-maleic anhydride copolymer in 212 g. of water. Agitation asapplied and the polymerization was carried out by heating at 86°-90° C.for 5 hours. The beads so formed were filtered, washed with water andthen dried 5 hours at 125° C. There was obtained 135 g. of white opaquepolymer in the form of spherical or spheroidal particles.

(C) The polymeric beads as prepared as set forth in A and B above weresulfonated as described in Example V B.

The product of part "A" shattered extensively during the sulfonationreaction as well as in the subsequent step of diluting the sulfuricacid, whereas the product of part "B" consisted substantially wholly ofperfect uncracked spherical particles.

EXAMPLE VI

A copolymer of styrene and 10 percent divinylbenzene prepared in thepresence of 40 percent butanol-2 as described in earlier examples wasfreed of butanol and water by steam distillation and oven drying at 125°C. for 6 hours. One hundred and six parts by weight of such resin wasadded to a mixture of 160 parts of ethylene dichloride and 200 parts ofmethyl chloromethyl ether. The mixture was held at 35°-40° C. and 66.7parts of aluminum chloride was added in portions during a period of twohours. Agitation was maintained at the same temperature range for aperiod of sixteen hours. Cold water was then added to decompose excesschloromethyl ether and aluminum chloride and the reaction product wassubjected to repeated washing with water, followed by draining of excessliquid. The chloromethylated product, obtained as a light yellow,granular product swollen with ethylene dichloride, amounted to 145 partson a dry basis and contained 18.5 percent of organically bound chlorine.

The aforesaid washed intermediate was stirred with 190 parts (by weight)of a 25 percent aqueous solution of trimethyl amine. The temperature washeld at 20° to 30° C. for two hours. The mixture was then heated toboiling and a mixture of residual ethylene dichloride and water wasremoved. Water was replaced as needed and the distillation was continueduntil no more ethylene dichloride appeared in the distillate. Thereaction product was washed and filtered. There remained 510 parts ofyellowish, opaque, granular material having an anion exchange capacityof 3.7 meq./g. (dry basis) or 0.9 meq./ml. wet basis. Its capacity todecolorize a crude sugar solution exceeded that of a commercialion-exchange resin technically employed for this purpose by 50-100percent. The volume increase upon conversion from the chloride to thehydroxyl form was found to be only 11.4% whereas the commercial resinshowed swelling values of 25-40 percent.

EXAMPLE VII

A solution of 2.00 grams of lauroyl peroxide in a mixture of 114.7 g. ofmethyl acrylate (containing 0.02 percent p-methoxyphenol inhibitor),25.3 g. of commercial divinylbenzene (containing 55.4 percent of actualdivinylbenzene) and 60.0 g. of 2-ethylhexyl acetate was suspended byagitation in 300 g. of an aqueous solution containing, besides water,5.0 g. of the ammonium salt of a styrene/maleic anhydride copolymer. Thewhole mixture was protected from air by maintaining an atmosphere ofnitrogen wihin the reaction vessel. The mixture was heated to 65° C. andheld at this temperature for three hours, during which timecopolymerization of the methyl acrylate and divinylbenzene took place,the droplets of liquid being converted to spherical particles of resin,still containing much of the 2-ethylhexyl acetate. The mixture washeated to 90° C. and held at that temperature for one hour, then cooled.Liquid was drained from the resin and the resin particles were washedwith water to remove residues of dispersing agent and minor amounts ofemulsion polymer. By returning the resin to the reaction flask, addingwater, boiling and collecting the condensed vapors, amounts up to 85percent of the 2-ethylhexyl acetate charged was recovered. The resin wasfiltered from the liquid and dried at 125° C. for five hours to removewater and residual 2-ethylhexyl acetate. The yield of dry resin was 124g.

An outstanding difference between the product of the preparation justdescribed and one prepared in the same way but omitting the 2-ethylhexylacetate was in the physical appearance of the beads. The preparationmade without 2-ethylhexyl acetate consisted of clear, transparentcolorless resin beads. The preparation made with the acetate esterpresent consisted of whitish beads ranging from transparent, but veryhazy, to translucent in appearance.

EXAMPLE VIII

A mixture of ethyl acrylate (114 grams), technical divinylbenzene (26grams of 55 percent concentration), 2-ethylhexyl acetate (60 grams) andlauroyl peroxide (2.0 grams) was added to an agitated solution of theammonium salt of a styrene/maleic anhydride copolymer (0.4 gram) inwater (298 cc.). The vessel was flushed with nitrogen and a slow streamof nitrogen maintained throughout the reaction. The batch was heated to65° C. for two hours and 90° C. for one hour. The opaque spherical beadproduct was then transferred to a column and steam passed through thecolumn downflow until the 2-ethylhexyl acetate was removed from thepolymer. The product was dried at elevated temperature, and 133 grams oftranslucent material was obtained.

One hundred parts of this product was mixed with three hundred parts ofdiethylenetriamine in a flask equipped with a short fractionatingcolumn. The batch temperature was gradually raised to 190° to 205° C.and maintained at this level for four hours. A fraction rich in ethylalcohol was collected in the receiver during this period. The resin wasisolated by dilution with water, filtration and washing to removesoluble material. The product (303 parts moist, 119 parts on a drybasis) consisted of opaque spherical particles with an anion exchangecapacity of 8.54 meq./gram dry.

EXAMPLE IX

A monomer solution was prepared by mixing 115 grams of methyl acrylate,25 grams of divinylbenzene (55.4 percent assay). 60 grams of di-n-butylsebacate and 2 grams of lauroyl peroxide. This solution was addedgradually with stirring to 300 ml. of water containing 2 grams of theammonium salt of a styrene/maleic anhydride copolymer. The mixture washeated at 65° C. for 3 hours and at 90° C. for one hour. The polymer wasobtained in bead form by filtration and was then heated at 125° for fivehours.

One hundred grams of this resin was heated to reflux with aqueous sodiumhydroxide (650 grams, 10 percent concentration) for 8 hours. During thistime, the polymeric ester and sebacate remaining in the beads werehydrolyzed. The resin was filtered and washed to remove solublematerials.

The resin was converted from the sodium to the hydrogen form bytreatment with a small excess of 5 percent aqueous hydrochloric acid.The yield was 168 grams of a white opaque material of perfect bead formhaving a solids content of 41.5 percent and a cation-exchange capacityof 9.7 meq./gram.

A sample of this resin was placed in an automatic cycling device inwhich the sample was exposed to 1 N sodium hydroxide, water, 1 Nhydrochloric acid and water in a 4-minute over-all cycle with aspirateddrainage of each reagent in turn. In a twenty-four hour test period only0.2 percent fines were generated by this osmotic shock treatment.Comparable resins prepared in the absence of dibutyl sebacate tended toform cracked and broken beads during the hydrolysis step anddisintegrated to the extent of 20 percent or more in the cycling testduring the twenty-four hour test period.

EXAMPLE X

The chlormethylated cross-linked styrene copolymer prepared as set forthin Example VI was drained to remove excess ethylene dichloride andwater. This product (332 grams, containing 57 percent of volatilematerial) was added to a flask containing 500 ml. of toluene equippedwith reflux condenser and agitator. Dimethylamine (41 grams) wasgradually added to the mixture at room temperature while stirring. After20 hours, water was added and a downward condenser was attached to theapparatus. The mixture was heated and distillation was continued untilthe organic solvents had been removed. The resin particles were isolatedby filtration. In order to place the resin in the fully regeneratedform, it was stirred with dilute sodium hydroxide for one hour and freedfrom excess caustic by washing. The yield of moist product was 332 gramsor 145 grams on a dry basis.

EXAMPLE XI

A methyl acrylate/divinylbenzene copolymer was prepared by suspensionpolymerization in the presence of 30 percent 2-ethylhexyl acetate andthe product was freed from the acetate ester by steam distillation or byextraction with a solvent such as methanol. The polymer was then driedat elevated temperature. The resin (100 grams) was charged to a pressurevessel containing 400 grams of 3-dimethylaminopropylamine-1. The closedvessel was heated at 170° C. for 5 hours, then cooled to roomtemperature. Water was added slowly, the product was filtered and washedthoroughly to remove excess amine. The yield of moist product was 348grams having a solids content of 37 percent and an anion-exchangecapacity of 4.74 meq./gram (dry basis).

EXAMPLE XII

The chlormethylated intermediate prepared as set forth in Example VI wasstirred with 225 ml. of water and 36 grams of dimethylaminoethanol. Themixture was heated to 74° C. for 2 hours and ethylene dichloride wasremoved by azeotropic distillation with water. There remained 231 gramsof opaque yellow solid having a moisture content of 60 percent and anitrogen content of 4 percent.

EXAMPLE XIII

A styrene copolymer with a nominal divinylbenzene content of 20 percent,prepared in the presence of 35 percent tert-amyl alcohol, was dried atelevated temperature to remove volatile material. The resin (92.5 grams)was mixed with technical sulfuric acid (398 grams, 98 percent) andconcentrated nitric acid (380 grams, 70 percent) was added dropwiseduring a period of 2 hours. Heat was evolved and the temperature wasmaintained at 45° to 50° C. The temperature was then gradually increasedto 80° to 83° C. and held at this level for 4 hours. After cooling, theresin was filtered and washed repeatedly with water to remove solubleacidic material. The product (138 grams) was dried at elevatedtemperature. Nitrogen, found 9.7 percent; calc. for mononitration 9.1percent.

The nitropolymer was evaluated in solvent swelling tests in comparisonwith nitrated styrene polymers containing as little as 1 percentdivinylbenzene cross-linking agent. The former material possessed a rateof solvent uptake several times that of the standard glassy typepolymer.

EXAMPLE XIV

    ______________________________________                                        Solution A                                                                    2-Methyl-5-vinylpyridine                                                                               98 grams                                             Divinylbenzene, technical (55%)                                                                        37 grams                                             Iso-octane               45 grams                                             Azo-bis-isobutyronitrile                                                                               1.35 grams                                           Solution B                                                                    Water                   183 grams                                             Sodium chloride (25% solution)                                                                         44 grams                                             Ammonium salt of styrene/maleic                                               anhydride copolymer (20% aqueous                                              solution)                5 grams                                              ______________________________________                                    

Solution "A" was added gradually with agitation to solution "B," therate of agitation being adjusted so as to form droplets of the desiredsize. The temperature was raised to 76° to 80° and the vigorous reactionwas moderated by cooling as needed. After five hours, the product wasisolated by filtration and washed repeatedly. Volatile material wasremoved by drying, beginning at 65° C. and completing the drying step at120° to 125° C. for 5 hours.

The product was obtained in the form of white opaque spherical particleshaving an anion-exchange capacity of 4.3 meq./gram dry.

The above formulation was based on a nominal divinylbenzene content of15 percent divinylbenzene and the iso-octane content in solution "A" was25 percent. In other preparations, the divinylbenzene content was variedfrom 5 percent to 25 percent and the iso-octane content from 15 percentto 35 percent with similar results. Because of the more highly developedpolar character of the pyridine type polymer, relatively smallquantities of the non-polar paraffinic solvent will suffice to inducephase separation.

Strong base resins of the quaternary type were obtained by treatment ofthe vinylpyridine polymers with alkylating agents, such as methylchloride, ethyl bromide, dimethyl sulfate, etc.

EXAMPLE XV

A mixture of styrene (120 grams), ethylene dimethacrylate (30 grams),tert-amyl alcohol (100 grams) and benzoyl peroxide (1 gram) was added toa solution of sodium chloride (5.4 grams) and 0.6 grams of carboxymethylcellulose in water (190 grams). The mixture was agitated and heated at88° C. for 5 hours. The product was filtered, washed with water anddried in an oven at 105° C.

The white opaque spherical product (140 grams) was added to a mixture ofethylene dichloride (565 grams) and methyl chloromethyl ether (200grams). Aluminum chloride (90 grams) was added in portions during a2-hour period with stirring while maintaining a temperature of 30°-40°C. After 10 more hours at the same temperature, cold water was added.The waste liquors were drained and several water washes applied.

The chloromethylated intermediate was obtained as light yellow sphericalparticles, moist with water and swollen with ethylene dichloride andcontaining 20.7 percent of chloride on a dry basis.

Conversion to anion-exchange resins was accomplished in a similarfashion as described in Examples VI, X, and XII.

EXAMPLE XVI

Methoxyethyl acrylate (116 grams, containing 0.05 percent1-methoxy-4-hydroxybenzene inhibitor), technical divinylbenzene (24grams, 58.2 percent assay), iso-octane (86 grams) and lauroyl peroxide(2.0 grams) were mixed and gradually added to an agitated solution ofpolyvinyl alcohol (0.5 grams) in water (290 grams). A slow stream ofnitrogen was passed through the vessel while the mixture was heated from67°-88° C. for 3 hours. The originally clear droplets became turbid aspolymerization progressed and white opaque beads were formed. Theproduct was filtered, washed and dried in an oven at elevatedtemperature. The yield was 137 grams.

EXAMPLE XVII

A mixture of N-vinylpyrrolidone (40 parts) and ethylene dichloride (10parts) and azoisobutyronitrile (0.5 parts) was prepared. Portions ofthis solution were mixed in a ratio of 7:3 with an alcohol or estertaken from the following group: secondary, tertiary and iso-amylalcohol, secondary butyl alcohol and 2-ethylhexyl alcohol and theacetate esters of the following alcohols, isooctyl, nonyl and2-ethylhexyl. The samples, including a control without additive, werepolymerized by exposure to 65° C. for one hour. The control was clearwhereas the other samples showed evidence of phase separation.

EXAMPLE XVIII

The nitrated styrene/divinylbenzene copolymer prepared according toExample XIII was stirred with concentrated hydrochloric acid (540 ml.).Granulated tin (20 mesh; 240 grams) was added during the course of 2hours. The temperature rose spontaneously to 78° C. The mixture was thenheated externally to 85°-95° C. for 24 hours. After removal of the acidthe polymeric product was washed several times with water and then fourtimes with aqueous sodium hydroxide (5 percent), or until the effluentwas clear. After further washing with water, there remained 250 l gramsof dark colored resin having a moisture content of 50 percent and ananion exchange capacity of 2.5 meq./gram (dry basis).

We claim:
 1. Cation exchange resin beads of macroreticular structure,high surface area, and lowered apparent density crosslinking essentiallyof a macroreticular crosslinked copolymer matrix with cation exchangefunctional groups bonded thereto, said resin beads having (1) anapparent density of at least 0.02 density units less than, and (2) asurface area much greater than gel-type ion exchange beads of the samecomposition, said beads resulting from the presence therein ofmicroscopic channels or voids of much larger dimensions than themicropores of gel-type ion exchange beads of the same composition, andwhich crosslinked copolymer matrix is prepared by copolymerizing amixture consisting essentially of (i) a monovinyl carbocyclic aromaticcompound or an ester of an acrylic or methacrylic acid, with (ii) apolyethylenically unsaturated monomer selected from the group consistingof a polyvinyl carbocyclic aromatic compound, an ester of a dihydricalcohol and an α-β-ethylenically unsaturated carboxylic acid, diallylmaleate, and divinyl ketone, the copolymerization being conducted whilethe monomers are dissolved in a phase separating amount of an organicliquid or mixture of organic liquids which is a solvent for saidmonomers but which is unable to substantially swell the copolymersresulting from copolymerization.
 2. Cation exchange resin beads of claim1 wherein the apparent density of the resin beads is not greater than1.0 g/ml.
 3. Cation exchange resin beads of claim 1 wherein themicroscopic channels or voids comprise at least about 17.5% by volume ofthe resin beads.
 4. In a process for preparing a cation exchange resinhaving a water insoluble matrix and cation exchange groups bondedthereto, the improvement comprising employing as said matrix a solidcopolymer of macroreticular structure which is permeated by smallchannels or voids into which liquids are able to penetrate, which matrixis prepared by copolymerizing a mixture consisting essentially of (1) amonovinyl carbocyclic aromatic compound or an ester of an acrylic ormethacrylic acid, with (2) a polyethylenically unsaturated monomerselected from the group consisting of a polyvinyl carbocyclic aromaticcompound, an ester of a dihydric alcohol and an α-β-ethylenicallyunsaturated carboxylic acid, diallyl maleate, and divinyl ketone, thecopolymerization being conducted while the monomers are dissolved in aphase separating amount of an organic liquid or mixture of organicliquids which is a solvent for said monomers but which is unable tosubstantially swell the copolymers resulting from copolymerization. 5.The process of claim 4 wherein said organic liquid is selected from thegroup consisting of an aliphatic hydrocarbon and an aliphatic alcohol.6. The process of claim 4 wherein said monomers dissolved in saidorganic liquid are suspended in an aqueous medium and polymerization iseffected in said suspension to obtain the copolymer in the form of resinbeads of macroreticular structure.
 7. The process of claim 4 whereinsaid cation exchange groups are sulfonic acid groups, saidmonoethylenically unsaturated monomer is a monovinyl carbocyclicaromatic compound, and said polyethylenically unsaturated monomer is apolyvinyl carbocyclic aromatic compound.
 8. The process of claim 4wherein said monoethylenically unsaturated monomer is styrene and saidpolyethylenically unsaturated monomer is divinylbenzene.